West Nile Virus (WNV) is one of the many neurotropic flaviviruses that is widely spread throughout the world, and continues to cause significant morbidity and mortality. In the US alone there were 24,000 cases of human WNV infection and 1000 fatalities since 2006. Both innate and adaptive immune components, including CDS, CD4 T cells and B cells contribute to WNV clearance and prevent infection of neurons. The adaptive immune components also form memory, which is the hall-mark for vaccination strategies. The generation of adaptive immunity is linked to innate activation, primarily via viral sensing by host pattern recognition receptors (PRRs), which in turn lead to ARC activation and generation of inflammatory mediators. One class of these early inflammatory mediators, type-l interferons (IFN-I) induce an anti-viral state in infected and neighboring cells. Many viruses, including WNV, developed potent IFN-I evasive strategies. Recent studies from our and other labs show that IFN-I can also exert profound influence on T cells responses, and generation of immune memory; but very little is known about the roles of specific pattern recognition receptors and the IFN-signaling in generating flavivirus-specific adaptive response. An understanding of this is critical for generating improved vaccines. We hypothesize that IFN-I signaling plays a critical role in generating WNV-specific adaptive immunity and that strategies to interfere with viral IFN-I evasive mechanisms should yield better vaccines. In Aim 1 we will define the role of dendritic cell signaling via RNA helicases and TLRs for generating WNV-specific CDS T cell responses. In Aim 2 we will examine the role of IFN-I signaling in the generation of WNV-specific CDS T cell responses. In Aim 3 we will assess the importance of the timing of IFN-I signals in programming T cell responses. Using the knowledge gained from these and the studies proposed in the other four projects of this U19, in Aim 4 we will modulate IFN-I signaling as means to enhance vaccination. Thus, this proposal will contribute to attainment of multi-project objectives of this U19.